Sea anemone 175967 226094555 2008-07-16T20:15:57Z Bob the Wikipedian 1531408 /* Gallery */ rem strawberry anemone...wrong order {{Taxobox | name = Sea Anemone | image = anemone_monterey_madrabbit.jpg | image_width = 250px | image_caption = Sea anemone at the [[Monterey Bay Aquarium]] | regnum = [[Animal]]ia | phylum = [[Cnidaria]] | classis = [[Anthozoa]] | subclassis = [[Hexacorallia]] | ordo = '''Actiniaria''' | subdivision_ranks = Suborders | subdivision = [[Endocoelantheae]]<br /> [[Nyantheae]]<br /> [[Protantheae]]<br /> [[Ptychodacteae]] | diversity_link = Actiniaria (family list) | diversity = 46 families }} [[Image:Haeckel Actiniae.jpg|thumb|right|The 49th plate from [[Ernst Haeckel]]'s ''[[Kunstformen der Natur]]'', 1904, showing various sea anemones classified as Actiniae]] '''Sea anemones''' are a group of water dwelling, [[predatory]] animals of the [[order (biology)|order]] '''Actiniaria'''; they are named after the [[anemone]], a terrestrial [[flower]]. As [[cnidaria]]ns, sea anemones are closely related to [[coral]]s, [[jellyfish]], [[tube-dwelling anemone]]s and ''[[hydra (genus)|Hydra]]''. ==Anatomy== A sea anemone is a small sac, attached at the bottom to the surface beneath it by an adhesive foot, called a basal disc, with a column shaped body ending in an oral disc. The mouth is in the middle of the oral disc, surrounded by tentacles armed with many [[cnidocyte]]s, which are cells that function as a defense and as a means to capture prey. Cnidocytes contain cnidae, capsule-like [[organelle]]s capable of [[Eversion|everting]], giving phylum Cnidaria its name&nbsp;<ref>{{cite book |author=Campbell N. & J. Reece |year=2002 |title=Biology |edition=6th ed |publisher=San Francisco: [[Pearson Education]]}}</ref>. The cnidae that sting are called ''[[nematocysts]]''. Each nematocyst contains a small vesicle filled with toxins—[[Actinotoxin|actinoporin]]s—an inner filament and an external sensory hair. When the hair is touched, it mechanically triggers the cell explosion, a harpoon-like structure which attaches to organisms that trigger it, and injects a dose of poison in the flesh of the aggressor or prey. This gives the anemone its characteristic sticky feeling. The poison is a mix of [[toxins]], including [[neurotoxins]], which paralyze the prey, which is then moved by the tentacles to the mouth/anus for digestion inside the gastrovascular cavity. Actinoporins have been reported as highly toxic to fish and [[crustacean]]s, which may be the natural prey of sea anemones. In addition to their role in predation, it has been suggested that actinoporins could act, when released in water, as repellents against potential predators. Certain [[clownfish]] are not affected by their host anemone's sting.<ref>http://sanctuaries.noaa.gov/pgallery/pgfagatele/living/living_03_100.html</ref> [[Image:Close-up of clone war of sea anemones.jpg|left|thumb|Sea anemones, ''Anthopleura sola'' engaged in war for territory]] The internal anatomy of anemones is simple. There is a gastrovascular cavity (which functions as a stomach) with a single opening to the outside which functions as both a mouth and an anus: waste and undigested matter is excreted through the mouth/anus, which can be described as an incomplete gut. A primitive nervous system, without centralization, coordinates the processes involved in maintaining homeostasis as well as biochemical and physical responses to various stimuli. Anemones range in size from less than 1¼&nbsp;[[centimetre|cm]] (½&nbsp;[[inch|in]]) to nearly 2&nbsp;[[metre|m]] (6&nbsp;[[foot (unit of length)|ft]]) in diameter.{{Fact|date=August 2007}} They can have a range of 10 tentacles to hundreds. [[Image:Anemone hermit crab 2 frames in one.jpg|[[Sea anemone|anemone]] and [[hermit crab]] developed [[symbiotic]] relationship |thumb|left|]] The muscles and nerves in anemones are much simpler than those of other animals. Cells in the outer layer (epidermis) and the inner layer (gastrodermis) have microfilaments grouped together into contractile fibers. These are not true muscles because they are not freely suspended in the body cavity as they are in more developed animals. Since the anemone lacks a skeleton, the contractile cells pull against the gastrovascular cavity, which acts as a hydrostatic skeleton. The stability for this hydrostatic skeleton is caused by the anemone shutting its mouth, which keeps the gastrovascular cavity at a constant volume, making it more rigid. ==Exploitation== The global trade in marine ornamentals is an expanding industry. In the early 1980s the estimated value of imported marine fish and invertebrates was US $24-40 million annually.<ref>Wood, E. 1985. "Exploitation of coral reef fishes for the aquarium trade." Report to the Marine Conservation Society. Marine Conservation Society, UK.</ref> Current estimates place that value at US $200-330 million,<ref>Chapman, F. A.; Fitz-Coy, S. A.; Thunberg, E. M.; Adams, C. M. 1997. United States of America trade in ornamental fish. Journal of the World Aquaculture Society. Vol. 28:1–10.</ref> with the USA accounting for 80% of the industry imports.<ref>Larkin, S.L.; Degner, R.L. 2001. The U.S. wholesale market for marine ornamentals. Aquarium Sciences and Conservation. Vol. 3:13–24.</ref> Despite advances and the expansion of [[aquaculture]], post-larval capture and rearing, the majority of marine ornamentals are collected in the wild as adults or juveniles.<ref>Shuman, C. G.; Hodgson, G.; Ambrose, R. F. 2005. "Population impacts of collecting sea anemones and anemonefish for the marine aquarium trade in the Philippines." Coral Reefs. Vol. 24:564-573.</ref> Anemones are susceptible to overexploitation due to their long life spans, slower growth rates, and lower reproductive rates than their resident fish, which are also affected because they settle exclusively and are restricted to specific host [[Sea anemones|anemones]]. The demand for these organisms is reflected in fishermen's catch records, which document the value they are paid per catch, and on average [[Sea anemones|anemones]] were valued at five times the value of the average value of [[anemonefish]], and ten times the value of the most abundant [[anemonefish]], and in fact only made up 4.1% of the total value of the catch. Research has shown that aquarium fishing activities significantly impact the populations of [[Sea anemones|anemones]] and [[anemonefish]] by drastically reducing the densities of each in exploited areas,<ref>Shuman, C. G.; Hodgson, G.; Ambrose, R. F. 2005. "Population impacts of collecting sea anemones and anemonefish for the marine aquarium trade in the Philippines." Coral Reefs. Vol. 24:564-573.</ref> and could also negatively impact [[anemone shrimp]], and any organisms obligately associated with [[Sea anemones|anemones]]. It should be noted that [[anemonefish]] can survive alone in captivity, as has been shown by multiple research efforts.<ref>Fautin, Daphne Gail. 1991. “The Anemonefish Symbiosis: What is known and What is Not.” Symbiosis. Vol. 10:23-46.</ref><ref>Shimek, R. (2004), p. 83. Marine Invertebrates. T.F.H. Publications, Inc. Neptune City, NJ.</ref> ==Ecology== [[Image:Common clownfish.jpg|thumb|left| [[Clownfish|Common (Ocellaris) clownfish]] (''Amphiprion ocellaris'') in their [[Heteractis magnifica|Magnificent sea anemone]] (''Heteractis magnifica'') home]] [[Image:Anthopleura sola is consuming Velella velella.jpg|right|thumb| ''Anthopleura sola '' is in process of consuming a By the wind sailor ''Velella velella'' [[jellyfish]]]] [[Image:Nudibranch attacking sea anemone 1.jpg|thumb|left|A nudibranch, species ''[[Aeolidia papillosa]]'' starts to eat a sea anemone]] The sea anemone has a foot which in most species attaches itself to rocks or anchors in the sand. Others also burrow into a stronger object. Some species attach to kelp and others are free-swimming. Although not [[plant]]s and therefore incapable of [[photosynthesis]] themselves, many sea anemones form an important facultative symbiotic relationship with certain [[cell (biology)|single-celled]] green [[algae]] species which reside in the animals' gastrodermal cells. These algae may be either [[zooxanthella]]e, [[zoochlorella]]e or both. The sea anemone benefits from the products of the algae's photosynthesis, namely [[oxygen]] and food in the form of [[glycerol]], [[glucose]] and [[alanine]]; the algae in turn are assured a reliable exposure to sunlight and protection from micro-feeders, which the anemones actively maintain. The algae also benefit by being protected due to the presence of stinging cells called nematocysts, reducing the likelihood of being eaten by herbivores. Most species inhabit tropical reefs, although there are species adapted to relatively cold waters, intertidal reefs, and sand/kelp environments. ==Life cycle== [[Image:Brooding sea anemone Epiactis prolifera 1.jpg|thumb|Asexual reproduction of sea anemone via [[budding]]]] [[Image:Sea anemone clones.jpg|thumb|left|Hundreds of anemones at low tide. They all are clones]] [[Image:Longitudinal fission of Anthopleura elegantissima.jpg|thumb|Sea anemone in process of cloning (longitudinal fission)]] Unlike other cnidarians, anemones (and other [[anthozoa]]ns) entirely lack the free-swimming [[Medusa (biology)|medusa]] stage of the life cycle: the [[polyp]] produces eggs and sperm, and the fertilized egg develops into a [[planula]] that develops directly into another polyp. A few anemones are parasitic to marine organisms. Anemones tend to stay in the same spot until conditions become unsuitable (prolonged dryness, for example), or a predator is attacking them. In the case of an attack, anemones can release themselves from the substrate and swim away to a new location using flexing motions. The sexes in sea anemones are separate for some species while some are [[hermaphroditic]]. Both sexual and asexual reproduction may occur. In sexual reproduction males release sperm which stimulates females to release eggs, and fertilization occurs. The eggs or sperm are ejected through the mouth. The fertilized egg develops into a [[planula]], which finally settles down and grows into a single anus. They can also reproduce asexually by [[budding]], [[binary fission]], which involves pulling apart into two halves, and pedal [[laceration]], in which small pieces of the pedal disc break off and regenerate into small anemones. [[Image:Anemone Crab.JPG|thumb|right|A [[porcelain crab]] living with an anemone, probably ''Entamacea quadricolor'']] ==Fossil record== Most Actiniaria do not form hard parts that can be recognized as fossils but a few fossils do exist; ''Mackenzia'', from the [[Middle Cambrian]] [[Burgess Shale]] of Canada, is the oldest fossil identified as a sea anemone. ==Stomphia== ''Stomphia'' is a genus of sea anemone which is called the "swimming anemone". It is very different from the rest because, though it anchors, it is able to swim away when it senses danger. On the bottom of the body is a suction cup-like part that is pushed in when the ''Stomphia'' anchors. It is then pushed out when the ''Stomphia'' needs to release itself. These anemones are able to react quickly to touch and immediately spring into action. They bounce away from the rock and away from the predator, and then swim by swinging their bodies back and forth. When the anemone is at a safe distance, it finds another rock and anchors onto it. ==Gallery== <gallery> Image:Ocean_reef.jpg|Sea anemones Image:Heteractis mag.jpg|A closed sea anemone Image:Deepsea anemone.jpg|Deep–sea anemone Image:Anemone.bristol.750pix.jpg|Sea anemones in a "[[nano reef|mini-reef]]" [[marine aquarium]] Image:Flytrapanenome.jpg|[[Venus flytrap sea anemone]] image:Beaded_Sea_Anenome_with_shrimp.JPG|A [[shrimp]] living with a [[Beaded sea anemone]] Image:Anemonefishfiji.jpg|Clown fish Image:Sea anemone in tidepools.jpg Image:Tide pools in santa cruz.jpg Image:Sea anemone and sea urchin.jpg </gallery> ==References== {{reflist}} ==External links== {{Wikispecies|Actiniaria}} {{Commonscat|Actiniaria}} *[http://web.nhm.ku.edu/inverts/carlgren_1949/actiniaria.html Order Actiniaria] *[http://www.actiniaria.com/ Actiniaria.com] * [http://www.starfish.ch/collection/anemones.html Photos of various species of Sea Anemones from the Indopacific] *[http://www.news.ucdavis.edu/search/news_detail.lasso?id=7438 Anemone Armies Battle to a Standoff] *[http://www.sciencenews.org/articles/20050604/fob2.asp Anemone Wars: Clone armies deploy scouts, attack tidally - unsuspected military tactics] *[http://users.bigpond.net.au/je.st/anemone/index.html Sea anemones look like sea flowers but they are animals of the Phylum Cnidaria] *[http://ricordea-farm.com/english/info.html Information about Ricordea Florida Sea anemones & pictures] [[Category:Anthozoa]] [[cs:Sasanky]] [[da:Søanemone]] [[de:Seeanemonen]] [[et:Meriroosilised]] [[es:Actiniaria]] [[eo:Maranemono]] [[fa:شقایق دریایی]] [[fr:Anémone de mer]] [[hr:Morska anemona]] [[io:Aktinio]] [[it:Actiniaria]] [[he:שושנות ים]] [[ka:აქტინიები]] [[lv:Jūras anemones]] [[hu:Tengeri anemona]] [[ml:സീ അനിമോണ്‍]] [[nl:Zeeanemonen]] [[ja:イソギンチャク]] [[pl:Ukwiał]] [[pt:Anêmona]] [[ru:Актинии]] [[sc:Orziara]] [[simple:Sea anemone]] [[sk:Sasanky]] [[sr:Морска саса]] [[fi:Merivuokot]] [[sv:Anemoner]] [[th:ดอกไม้ทะเล]] [[tr:Deniz laleleri]] [[uk:Актинії]] [[zh:海葵]]